Ravichandran Ashwin’s hallmark as a bowler in this format is the impact he makes by restricting runs.

Measuring the economy rate of a batsman relative to the average economy rates in every match he plays in is an idea pioneered at Impact Index. This number, between 0 and 5, taken across a career, provides the clearest picture of the impact a batsman had on account of his economy rate.

So, the varying standards of its time (when the analysis is done across eras) or of the conditions (say, the tournament economy rate during IPL 2 at South Africa would be different from the tournament economy rate in other years due to the conditions) is taken care of in this system, and therefore provides the truest picture as far as economy rate comparisons go.

Here are the bowlers with the highest Economy Rate IMPACT numbers over the last 4 years of IPL (minimum 15 matches).

Ravichandran Ashwin’s hallmark as a bowler in this format is the impact he makes by restricting runs.

Muttiah Muralitharan is the only bowler who comes close to Ashwin’s ability to choke runs. It is not a coincidence that they played for the same side – CSK – which has been the highest impact side in IPL history.

Lasith Malinga is notable for his ability to take wickets (especially demolishing the lower-order) but in this format, the inability of batsmen to score freely off him is his key differentiator.

Daniel Vettori is by a distance the most successful non-subcontinental spinner in the IPL, and his Economy IMPACT his most significant quality.

Dale Steyn - one would expect him to always be a serious wicket-taking bowler, but in this format, he is not. It is his outstanding Economy IMPACT that makes him significant.

It is interesting how the first two bowlers are so close to each other and the next three in a distinct cluster too in terms of Economy IMPACT numbers. It is also curious how lethal wicket-taking bowlers in other formats, like Muralitharan, Malinga and Steyn, make a mark in this format more for their ability to restrict batsmen from scoring.

MI strangling KKR comprehensively for 67 all out in 16 overs had a lot to do with Pollock’s quintessentially measly bowling – as he set the tone right from the beginning. When MI batted, Jayasuriya’s 48 in 17 balls further added weight to Pollock’s bowling.

The Pollock-Jayasuriya combo again. CSK’s ostensibly respectable total of 156 had 4 overs of Pollock magic, as only 9 runs could be scored off them. Achieving this right at the top had its impact on CSK – the total was nowhere near enough on this pitch - MI knocked off the runs 14 overs, with Jayasuriya making 114 in 48 balls.

Fidel Edwards opened the bowling, took no wickets but KKR finished at just 101. He bowled just one maiden over, but in the remaining three overs, he gave away just 6 runs. DC knocked off the runs in 14 overs, which further provided context to Edwards’ outstanding performance.

A remarkable all-round performance from Brad Hodge resulted in the biggest victory KTK achieved in their short IPL existence. RR were knocked out for 97 in 14 overs – in 4 of which they were traumatised by Hodge’s off-breaks – and a batting line-up consisting of Dravid, Watson and Rahane just collapsed without a fight, as Hodge ran through the middle-order.

MI managed 154 in their 20 overs, with a standout bowling performance from RP Singh – he was just impossible to get away. Adam Gilchrist made a mockery of the total with a 109 off 47 balls, off bowlers like Pollock, Nehra, Bravo and Jayasuriya, which made RP Singh’s effort even more commendable.

MI’s score of 160 on a DY Patil pitch would prove to be more than adequate – which made Rahul Sharma’s bowling effort even more creditable. With batsmen like Blizzard, Tendulkar, Rohit Sharma, Pollard and Symonds in front of him, Sharma managed to give away just 7 runs.

On a helpful Bloemfontein pitch, a powerful DD line-up was restricted to just 120. Then, Sangakkara played a captain’s innings as KXIP won in the last over. Nehra’s spell of 1-6 in 4 overs was not even remotely matched by any other bowler in his team, otherwise the story might have been different.

After a rollicking 221-3 by KXIP, RR would have hoped for a good start. Irfan Pathan’s bowling at the top put paid to that. Eventually he was the one bowler they could not get away (in fact, the only bowler in the match who gave less than 7 runs an over). Pathan’s impact was considerable – in fact, despite taking just 1 wicket, his bowling impact crossed 4 comfortably – not a common occurrence at all.

An imposing 211 by RR on a seeming featherbed appeared a completely different proposition as Amit Singh’s bowling at the top prevented a formidable batting line-up (comprising of Sangakkara, Katich, Jayawardene, Yuvraj and Irfan Pathan) from getting set, as they folded up for an unworthy 133.

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